Graphene, a one-atom-thick planer sheet of sp2 bonded carbon atoms, holds promise for optoelectronic applications due to its unique properties of high carrier mobility at room temperature, with reported values in excess of 15,000 cm2V−1s−1, optical transmittance of about 97.9% for white light and flexibility (see Novoselov et al. (2005); Geim et al. (2007); and Novoselov et al. (2004)). However, the zero bandgap of the graphene has presented a major hurdle to its electronic applications, especially in digital electronics. While small sub-eV bandgaps have been obtained in graphene nanoribbon (“GNRs”) or graphene nanomesh (see Han et al. (2007); Bai et al. (2010); and Todd et al. (2009)), it is often at the cost of significantly reduced mobility due to the presence of charge fluctuation associated with various defects primarily from the uncontrolled GNR edges and the interfaces. In the meantime, considerable efforts have been made recently to attach photosensitive materials to graphene to form hybrid structures with selected ranges of photoabsorption (see Kamat (2011)). For example, a TiO2/GO hybrid was synthesized using hydrolysis in combination with hydrothermal treatment as a photocatalyst for photodegradation of rhodamine B molecules (see Liang et al. (2010)). On the other hand, CdSe/ZnS core/shell nanocrystals were spun-coat onto the graphene layers of mechanical exfoliated flakes, for efficient energy transfer from photo-excited CdSe/ZnS nanocrystals to graphene with fluorescence intensity quenched by a factor of about 70 (see Chen et al. (2010)). The hybrid structure of ZnO/graphene is of particular interest because of its superior wavelength selectivity and charge mobility, both are critical to applications of ultraviolet (“UV”) sensors (see Chang et al. (2011)), electron emitters (see Kim et al. (2011)), and many other applications (see Hwang et al. (2010) and Chung et al. (2010)). Interesting progress has been made in fabrication of hybrid nanostructures of ZnO/graphene including chemical vapor deposition (“CVD”) of ZnO nanowires and nanowalls on CVD graphene (see Kumar et al. (2011)), solution synthesis of ZnO nanorods on graphene flakes casted on silicon or glass substrates to form hybrid ZnO/graphene thin films (see Chang et al. (2011)), and solution synthesis of ZnO nanorods on CVD graphene transferred on glass or poly(ethylene terephthalate) substrates (see Park et al. (2009)). The required high temperature in the CVD growth of ZnO nanostructure on graphene is not preferred since it will prevent use of many technologically important substrates such as glass and plastic (see Kumar et al. (2011)). In addition, the high ZnO growth temperature may lead to formation of defects on graphene and hence degrade the conductivity of graphene and possibly the interface between graphene and ZnO, both are crucial to optoelectronic applications. The solution method (see Vayssieres (2003); Xu et al. (2008); and Yang et al. (2006)) has a unique advantage for the large-scale synthesis of hybrid nanostructures of ZnO/graphene at low temperatures and low costs. However, the reported solution process requires ZnO seeding layers to initiate nucleation of ZnO on graphene. Generation of the seeding layer involves additional fabrication and lithography steps in vacuum and at elevated temperatures up to 180° C. (see Park et al. (2009) and Yi et al. (2011)). Furthermore, it should also be noted that aligned ZnO nanowire array directly grown on graphene possesses advantages of optimized UV absorption and superior photo-carrier transfer/transport, both are crucial to high-performance UV detectors. Unfortunately, such a configuration of vertically aligned ZnO nanowire arrays has not been obtained in solution processes, in which the samples are typically immersed in the solution in a face-up configuration (see Zhou et al. (2012) and Yang et al. (2011)).